A variety of types of machines and processes exist for making multi-folded paper towels and the like by producing stacks of interfolded sheets having a desired folded width.
The “interfolding” is accomplished by partially overlapping the individual sheets in the stack during the folding process. The overlapping and folding is carried out in such a manner that, with the stack loaded into a dispenser when a sheet is pulled out of the dispenser, a panel of the following sheet is also pulled out of the dispenser to facilitate the next user in pulling the next towel from the dispenser. Multi-panel interfolded sheets of this type often have three panels forming a Z-folded shape or four panels having a W-folded shape. Other folded shapes and numbers of panels are sometimes used.
In one approach to forming such stacks of interfolded multi-panel sheets, a single web of material is fed sequentially through a sheet-cutting-and-overlapping arrangement and then to an interfolding arrangement. The web of sheet material is fed along a single path which extends through the sheet-cutting-and-overlapping arrangement to the interfolding arrangement, for forming a desired interfolded pattern of sheets having a desired folded panel width, sheet length, and folding pattern.
The sheet-cutting-and-overlapping arrangement is configured for generating a stream of sheets having the desired length which are fed along the path to the interfolding arrangement. The stream of sheets moves through the interfolding arrangement at an interfolding feed speed. The sheet-cutting-and-overlapping arrangement generates an overlap speed, of the stream of sheets along the path upstream from the interfolding arrangement, which is higher than the interfolding feed speed.
Due to the difference between the interfolding feed speed and the overlap speed, as each sheet in the stream of sheets transitions from the sheet-cutting-and-overlapping arrangement to the interfolding arrangement, a portion of the sheet forms a bulge and the trailing edge of the sheet eventually pulls free in such a manner that the leading edge of the following sheet along the path will slide under the preceding sheet by a desired overlap amount, which is often selected to be substantially equal to the desired folded width of the interfolded stack. With successive sheets in the stream of sheets overlapped in this manner, the interfolding arrangement then folds the overlapped sheets in such a manner that the interfolded stack is produced.
One example of an interfolding apparatus of the type described above is shown in commonly assigned U.S. Published Patent Application No. US 2007/0082800, to Kauppila. The disclosure and teachings of the Kauppila application are incorporated herein in their entireties by reference.
In prior interfolding apparatuses and methods that utilize a stream of sheets cut from a single web of material fed along a single path, parameters such as the sheet length, the overlap length, folded shape, and the folded width of the interfolded stack are all parameters that are set by the configuration of mechanical components within the interfolding apparatus. For example, in the Kauppila reference, the apparatus includes a cutting roll interacting with a lap roll for cutting the web of material into sheets of the desired lengths, and feeding those sheets to a pair of interfolding rolls at an overlap speed. The configuration of the interfolded stack, and the shape of the folded sheets therein, are set by physical parameters such as the relative diameters and rotational speeds of the cutting roll, the overlap roll, and the interfolding rolls. With such an arrangement, if it is desired to change from a three-panel, Z-shaped, folded shape having a given width, to a four-panel, W-shaped, folded shape, having the same folded width as the three-panel product, it is typically necessary to physically replace the lap roll and cutting roll with rolls having a different diameter to produce cut sheets of a different length and to move those sheets along the path at a different desired overlap speed which is dependent upon the peripheral speed of the overlap roll. The necessary disassembly and reassembly of the interfolding apparatus with different components, to switch from a production run of three-panel towels to a production run of four-panel towels, for example, involves considerable expenditure of time and effort which it would be desirable to eliminate.
In an attempt to address this problem, U.S. Published Patent Application No. US 2007/0203007, to De Matteis proposes the use of an interfolding machine having a modular structure in which groupings of the rollers are mounted together in a common mounting structure in such a manner that they can be removed and replaced as a module, independent from a main portion of a frame of the interfolding apparatus. This approach adds considerable weight, cost and complexity to the overall construction of the interfolding apparatus and would still appear to require a significant amount of machine downtime and non-productive manpower cost for changing from one module to another.
It is desirable, therefore, to provide an improved interfolding apparatus and method which is capable of producing multiple interfolded patterns from a stream of sheets fed from a single web of material, which avoids one or more of the problems discussed above.